The present invention relates to a method of directing an optical receiver toward a light source and an apparatus for practicing the method. More particularly it concerns a method and an apparatus for directing an optical receiver toward a light source, where the method includes the use of a plurality of light detectors arranged around the receiver's optical axis to check how the light hits the light detectors relative to the optical axis. The light source may for example be an optical transmitter.
It is known to use an optical receiver in a communication system. For the receiver to be able to function as good as possible it is vital that the receiver is directed toward the light source. I.e. the receiver's optical axis is directed toward the light source. Such a directing, which in the specialist environment is also referred to as alignment, is according to prior art performed by the receiver being manually at least coarsely directed toward the light source. Coarse directing means a directing where the receiver is directed toward the light source with such accuracy that the light beam from the light source hits the receiver optics. Such coarse directing can be time consuming and costly and will have to be repeated if the receiver's pointing direction comes out of position relative to the light source.
Apparatuses that will be able to undertake a fine directing such that the receiver's optical axis is aligned with the light source's optical axis, as soon as the receiver is coarsely directed, are known. The apparatuses' fine directing may be based on measuring where the light hits relative to the receiver's optical axis.
Such an apparatus is known from the publication EP 0653 852 A1 describing an optical transceiver or transmitter-receiver wherein two opposing transceivers must be directed toward each other manually before a fine directing or aligning of the optical axes are undertaken automatically. The coarse directing is undertaken by means of a sighting device allocated to the transceiver.
Another such apparatus is known from the publication US 2002/0196506 A1 describing an apparatus for optical transmission of data between two opposing transceivers. The apparatus includes two telescopes directed toward each other and provided with inter alia deformable mirrors being able to compensate for varying atmospheric conditions such as fog and precipitation, and for aberration that might affect the light being sent between the transceivers. The transceivers according to US 2002/0196506 A1 must be manually directed toward each other.
A transceiver with an optical receiver with driving means for scanning, focusing means and an optical transmitter, connected to the receiver, is known from the publication EP 0911995 A2.